The present invention relates generally to agricultural machinery and, more particularly, to improvements in measuring moisture in crops. The invention provides a moisture measuring device as well as a method for measuring moisture of the crop material in harvesting machines.
It is known in the art that moisture sensors can be used in agricultural machines to precisely measure the quantity of harvested grain, especially corn, based upon a measurement of the harvested crop material moisture. For example German Patent Application DE 41 05 857 provides a moisture measuring device which uses a bypass system to continuously determine the moisture of the harvested crop material. Furthermore, U.S. Pat. No. 5,616,851 discloses a moisture sensor which operates by accumulating a quantity of material to be measured in a measuring chamber, then performing the measurement and returning the measured material to the stream of crop material prior to beginning a new measuring cycle. Arranging continuously operating moisture sensors directly in the path of conveying the crop material has also been attempted. For example, a moisture sensor has been arranged in a grain tank filling screw, instead of a spiral, or in the grain tank. These locations for mounting the sensors were selected to be independent of the throughput of crop material because throughput fluctuations affect the accuracy of the moisture measurement. However, because a sensor in the filling screw interferes with the conveying of material and a sensor in the grain tank always allows only one measurement per grain tank, both systems were commercially unsuccessful.
A microwave sensor which is constructed as a smooth sensor and is capable of determining, by use of microwaves, the moisture content of the crop material moving past the smooth sensor is known in the art from German Patent Application DE 196 48 126. The microwave sensor disclosed is relatively expensive and is also structurally elaborate, as the environment must be shielded from the microwaves.
All moisture sensors known from the state of the art must be calibrated to obtain accurate moisture values. There is a distinction between calibration related to the material to be measured, which depends upon the type of crop material, and calibration related to processing, which is determined by the density of the material to be measured, the quantity of material conveyed and the conveying members. For calibration related to the material to be measured, there are provided calibrating curves which can be accessed by the user of the moisture measuring device. These curves are in each case valid for certain temperatures of material. However, the need for processing-related calibration is, in practice, bypassed by setting up measuring points with at least temporarily constant measurement conditions. These measuring points do not always ensure constant measurement conditions. Therefore, errors arise, which multiply if further processing-related error sources of measurements, such as fouling of the sensor, are ignored. Under such conditions, the accuracy of the moisture value depends on the harvesting machine operator""s care and understanding for the concerns of the moisture measuring device, which cannot always be presupposed.
It is an object of the present invention to provide an improved moisture measuring device which minimizes the above described drawbacks of state of the art moisture measuring devices.
In accordance with the present invention there is provided an agricultural machine including a moisture measuring device having a moisture sensor for measuring moisture of the crop material in the machine, and a sensor state monitoring device interconnected with the moisture measuring device.
The object of the present invention is achieved by combining the moisture measuring device with a sensor state monitoring device. The combination of the moisture sensor with a sensor state monitoring device makes it possible to detect error when determining the moisture signal and to display such errors to the driver of the harvesting machine. Furthermore, this combination makes it possible to perform correction measures or calibration. The calibration measures which were previously necessary can be largely dispensed with because the sensor state monitoring device accomplishes a good proportion of the calibration work in an automated fashion. Moreover, the reliability of the moisture measuring device is improved and the driver is relieved of recurring routine work and checks.
In accordance with another aspect of the present invention there is provided a method for determining a moisture value of crop material via a moisture measuring device in an agricultural machine, including the steps of: sensing a moisture value in the crop material via a moisture sensor; transmitting the moisture value to an electronic analyzer; operating the electronic analyzer to offset the moisture value against a calibration-dependent correction value; further processing the offset moisture value for analysis purposes; and determining the correction value at least, in part, as a function of a working state of the machine.